Sewing machine driving and stopping mechanisms



SEWING MACHINE DRIVING AND STOPPING MEGHANISMS 9 Sheets-Siles a 2 Ema July 10, 1962 a 0 6 w w a M M 8 54 i r ll 6 5 M u 8 6 m 0 L w 6 1 w July 28, 1964 A. R. COPITHORNE ETAL 3,142,278

SEWING MACHINE DRIVING AND STOPPING MECHANISMS Filed July 10, 1962 9 Sheets-Sheet 3 July 28, 1964 A. R. COPITHORNE ETAL 3,142,273

SEWING MACHINE DRIVING AND STOPPING MECHANISMS Filed July .10, 1962 9 Sheets-Sheet 4 July 28, 1964 A. R. COPITHORNE ETAL 3,142,273

SEWING MACHINE DRIVING AND STOPPING MECHANISMS Filed July 10. 1962 9 Sheets-Sheet 5 2 5 mu m a 3 4 J I 6 a J I 5 Q a H M A Q 2 Q 6 M M Q w w U July 28, 1964 A. R. COPITHORNE ETAL 3,142,278

SEWING MACHINE DRIVING AND STOPPING MECHANISMS Filed July 10, 1962 9 Sheets-Sheet 6 July 28, 1964 A. R. COPITHORNE ETAL 3,142,278

SEWING MACHINE DRIVING AND STOPPING MECHANISMS Filed July 10, 1962 9 Sheets-Sheet 7 July 28, 1964 A. R. COPITHORNE ETAL SEWING MACHINE DRIVING AND STOPPING MECHANISMS Filed July 10, 1962 9 Sheets-Sheet 8 y '1964 A. R.'COPITHORNE ETAL 3,142,278

SEWING MACHINE DRIVING AND STOPPING MECHANISMS Filed July 10, 1962 9 Sheets-Sheet 9 r *0 o w WL.

United States Patent 3,142,278 SEWING MAHINE DRIVING AND STOPPING MECHANISMS Alton R. Copithorne, Rowley, Raymond A. De Vita, Winchester, Blandford W. Greene, Manchester, George J. Musial, Lynnfield, and .i'oseph R. Ioannilli and Robert G. Akeriey, Beverly, Mass, assignors to United Shoe Machinery Corporation, Flemington, N.J., a corporation of New Jersey Filed July 10, 1962, Ser. No. 208,847 17 (Ilaims. (Cl. 112-219) This invention relates to improvements in driving and stopping mechanisms and is herein illustrated as embodied in a lock stitch shoe sewing machine of the type disclosed in United States Letters Patent No. 1,233,539, granted July 17, 1917, upon an application of F. Ashworth.

Machines of the type described in the patent noted are arranged to form lock stitch seams in shoe outsoles or similar tough, thick materials and the parts of a machine of this nature are heavily constructed for actuating a curved hook needle and a curved awl to penetrate the material of the work and to form a thread seam by carrying loops of needle thread through the work and interlocking them with loops of locking thread in a uniform and reliable manner. Driving and stopping mechanisms for the purpose intended are arranged to control the operation of a sole stitching machine in an easily regulated manner with a minimum of effort on the part of an operator and to bring the machine to rest at a predetermined stopped position while running normally at a relatively high speed in as brief an interval of time as possible with the needle and awl disengaged from the work, and preferably with the final stitch of a seam completed and drawn securely into place. Not only is it difiicult to bring such machine to rest with accuracy at a predetermined stopped position, but the amount of energy required to be dissipated in bringing the machine to rest while operating under full speed conditions is of a magnitude capable of subjecting the operating parts of the machine to excessively heavy stresses unless properly controlled. To assist in dissipating energy in the shortest possible time, the machine of the prior patent employs a. slow speed driving mechanism, which first acts as a friction brake and then causes the machine to be turned over at slow speed to a precise stopped position. To determine the stopped position accurately a main sewing shaft in the prior machine has secured to it a cam formed with a shoulder arranged to be engaged by a rigid stopping dog pivoted on the machine frame, the stopping dog being held out of the path of the cam during sewing operations and before being engaged by the cam shoulder the cam is utilized to shift the stopping dog bodily within the path of the cam in order to perform certain auxiliary operations, such as raising a work clamping presser foot from the work and rendering a sewing thread tension inoperative, so that the work may be removed from the machine without obstruction.

The auxiliary operations in the machine are performed just before the sewing shaft is brought to rest in its predetermined stopped position, the energy for the purpose being provided by the inertia of the machine parts. To avoid damage to the machine and disfiguration or injury to the work being operated upon while removing it from the machine the shoulder must be engaged firmly but not violently with the stopping dog. Because the amount of energy to be dissipated may vary from time to time the shoulder on the cam may not be brought fully into engagement with the stopping dog or the shoulder may rebound from the dog before the sewing shaft comes to rest, the slow speed driving mechanism being so ad- 3,142,278 Patented July 28, 1964 justed that it becomes inoperative before the desired stopped position is reached. Because the slow speed driving mechanism depends upon a friction clutch, full engagement with the stopping dog is thus insured only by careful adjustments. Under changing conditions, such as moisture content of the air, contamination by oil or other unforeseen circumstances affecting friction surfaces, the operation of the slow speed driving clutch may be inadequate and it is usually necessary to make adjustments frequently according to the changing conditions.

An object of the present invention is to provide a driving and stopping mechanism for use with a heavily constructed sewing machine of the type referred to, in which frequent adjustments are not required and by which uniform stopping results are obtainable under all practical operating conditions. Other objects are to improve operation of driving and stopping mechanisms for heavily constructed sewing machines requiring reliable and accurate stopping and to avoid dependency on friction surfaces, not only for stopping mechanisms but also for driving mechanisms, especially when used with slow speed driving mechanisms to reduce rotation of a sewing shaft to a uniform speed regardless of the rate before stopping is initiated.

To the ends stated the present machine is provided with stitch forming devices, a main sewing shaft for actuating such devices, and a hydraulic displacement unit mechanically connected to the main sewing shaft and provided with an inlet conduit and an outlet conduit selectively connected to a flow restricting circuit to enable the speed of rotation of the shaft to be reduced and the stitch forming devices when operating at normal running speed to be brought to rest at a predetermined stopped position determined by a positive mechanical stop within a single rotation of the sewing shaft. Important advantages of such construction are that ample stopping and energy absorbing ability are ensured to bring the sewing shaft to rest within a single rotation of the sewing shaft without subjecting the operating parts to excessively heavy stresses regardless of operating conditions, unreliability of adjustments and difiiculties with contamination common to the use of unreliable friction surfaces being eliminated.

Further features of the invention above noted reside in the use of a variable hydraulic energy supply connected to the inlet conduit for the hydraulic displacement unit and also in the use of a pressure compensated operator controlled valve, acting to cause the same uniform volume of fluid to flow through the inlet conduit regardless of the resistance offered by the displacement unit, and to enable rotation of the sewing shaft while rotating at normal sewing speeds to be retarded smoothly until an exact position of rest is reached from any speed up to a possible maximum. In this feature of the invention the hydraulic energy supply includes a pump and the valve by-passes a fixed proportion of the fluid supplied by the pump, so that when the effort is exerted by the variable energy supply is being reduced the valve connects the flow restricting circuit to the outlet conduit of the displacement unit in ample time for the desired results.

Preferably, the hydraulic energy supply consists of two pumps, a low pressure relief valve being connected to the outlet of one to enable it to be disabled below a speed of operation approximating that provided by the slow speed friction clutch drive of the prior machine, while the other one provides high pressure and continues to drive the motor at slow speed after the first pump is rendered ineffective by the relief valve.

These and other features of the invention, as hereinafter described and claimed, will be apparent to those skilled in s3 the art from the following detailed specification, taken in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view looking from the front of portions of the sewing head in a machine embodying the features of the present invention;

FIG. 2 is a fragmentary perspective view in rear elevation on a somewhat larger scale of the machine shown in FIG. 1;

FIG. 3 is a detail view looking from the left side of the machine and showing on a further enlarged scale a set of treadle control connections actuated by the operator of the machine;

FIG. 4 is another detail side view, looking from the left, on a still further enlarged scale of other portions of the treadle connections showing the parts with the machine taken in positions of rest at the end of a seam;

FIG. 5 is a detail view in front elevation of a stopping dog latch shown in FIG. 4;

FIG. 6 is a left side view of the operator actuated connections shown in FIG. 4, but taken with the parts in positions assumed just before the rest position of FIG. 4;

FIG. 7 is a detail view in front elevation of the latch shown in FIG. 5 when the position of FIG. 6 is reached;

FIG. 8 is a rear detail view of a hydraulic manifold block shown in FIG. 2;

FIG. 9 is an enlarged sectional detail view of a volume compensated hydraulic speed control valve shown in FIG. 2;

FIG. 10 is a similar enlarged sectional view of a magnetic and pilot controlled pressure relief valve, which is mounted on the manifold block of FIG. 8;

FIG. 11 is a schematic hydraulic system diagram of the driving and stopping mechanism employed in the machine; and

FIG. 12 is an electrical circuit diagram employed in the control for the hydraulic system of the machine.

The sewing machine illustrated in the drawings is an outsole lock stitch curved hook needle machine, similar in many respect to that disclosed in United States Letters Patent No. 2,271,611, granted February 3, 1942, upon application of F. Ashworth et al., except that the operating parts of the machine are constructed comparatively heavily and the intended speed of rotation in the sewing shaft is above a rate in excess of 1,000 r.p.m.

The driving and stopping mechanism disclosed in Patent No. 2,271,611 is arranged to impart rotation to a main sewing shaft in that machine by means of a high speed friction clutch forming a part of a driving mechanism, a graduated speed control below the maximum being obtained by frictional slippage of clutch surfaces. The machine is brought to a predetermined rest position after operating at normal sewing speed under the control of the operator by a friction brake comprising a part of a slow speed driving mechanism, which slow speed mechanism first causes slippage to reduce excess speed and then operates to drive the machine through a fraction of a turn to its rest position where the slow speed mechanism is disconnected and the sewing shaft is permitted to stop without excessive shock or jar. To locate accurately its predetermined position of rest the main shaft of the machine is provided with a positive mechanical stop comprising a cam on the sewing shaft, having an abrupt radial shoulder, which is brought into engagement with a stopping dog pivoted on a fixed shaft in the machine frame and held out of the path of the cam by the control treadle during normal sewing operations.

The present machine has, besides its conventional stitch forming devices and its main sewing shaft for actuating these devices, stopping means including a hydraulic displacement unit mechanically connected to the main sewing shaft and arranged to dissipate the energy required to bring the sewing shaft to rest in a predetermined stopped position. As illustrated, the energy is dissipated by the use of a flow restricting circuit connected for operation to an outlet conduit for the hydraulic displacement unit, so that the stitch forming devices may be brought to rest within a single full rotation of the sewing shaft and a hydraulic energy supply may be connected with the inlet of the displacement unit to drive the machine. For bringing the sewing shaft to rest accurately the stopping means includes also a positive stop, similar to that employed in the prior machine, comprising a shoulder on a cam is engaged with a rigid stopping dog or pawl. The advantages of the improved driving and stopping mechanisms are that control of energy dissipation hydraulically by a flow restricting circuit is more reliable and less critical than the use of friction between mechanical surfaces in clutches or brakes, wherein the coefficient of friction is likely to change drastically with slight variations of pressure, or the presence of contamination or heat in the friction surfaces.

Referring more particularly to the drawings, the stitch forming and work feeding devices of the machine include a curved hook needle 2, a curved work penetrating awl 4, a work support 6, a presser foot 8, a shuttle 10 containing a supply of locking thread 12 and a take-up 14 for controlling the needle thread as it is drawn from the shuttle 10 into the work, together with a loop of interlocked locking thread to complete each stitch. The stitch forming and work feeding devices are actuated by a main sewing shaft 16 having secured to its right hand end a hand wheel 18.

For determining the position accurately and positively at which the machine is brought to rest with the needle and awl free of the work, for raising the presser foot from engagement with the work and for performing other auxiliary operations, so that the work may be withdrawn readily from the machine, the sewing shaft 16 has secured to it the shouldered cam, designated 20 (see FIG. 4). Cooperating with the cam is the stopping dog, indicated at 22 pivotally mounted upon a rocking sleeve 24 supported by a shaft 26 fixed in a portion of a machine frame 28 and arranged substantially parallel to the main sewing shaft 15, so that the stopping dog may move laterally into and out of the path of the cam 20 and also may be shifted bodily within the path of the cam shoulder. When the stopping dog is shifted by engagement with the cam, connections between the stopping dog and the presser foot unlock it and lift it from clamping engagement with the work and the other auxiliary operations are performed.

The stopping dog is shifted bodily by the cam 20 while the dog is within the path of movement, there being a set of control connections running between the stopping dog and an operator controlled treadle 30 (see FIGS. 2 and 3). To move the dog laterally into the cam path and to bring the machine to rest the treadle 30' is raised yieldingly by a spring 32 stretched between a fixed portion of the machine frame and the treadle. When the treadle is depressed the stopping dog is moved out of the path of the cam and the main sewing shaft is rotated. When the treadle is released the spring raises the treadle and the dog moves into the cam path. To prevent excessively violent engagement with the stopping dog after being moved into the path of the cam 20 in the machine of the prior patent, especially when the slow speed driving mechanism is unable to reduce the speed of rotation of the sewing shaft to a safe value, the train of connections between the stopping dog and the control treadle includes a vibrating lever and a lock bolt connected to the treadle in such manner that entry of the stopping dog into the path of the cam 20 is prevented until the lock bolt has entered an opening in the vibrating lever of the slow speed driving mechanism. In this way the stopping dog is held from entry into the path of the cam until after the slow speed driving mechanism has been set in operation for a substantial portion of a full rotation.

Because no friction clutch is used for the slow speed driving mechanism in the present machine and instead, a hydraulic displacement unit is utilized to drive the machine, a flow restricting circuit is connected for operation to the outlet conduit of the displacement unit, whereby a much more reliable stopping operation is insured, the flow restricting circuit being rendered operative at the same time that the stopping dog enters the path of the cam, thus simplifying the connections required to control the stopping operation.

The control connections of the illustrated machine, as shown in FIGS. 2 to 7, inclusive, include a treadle rod 34 pivotally connected between the treadle and a forwardly extending arm of a lever 36 fulcrumed by a pivot 38 (FIG. 3) on a fixed portion of the machine frame. The lever 36 also is pivotally connected to the lower end of a vertical rod 40 having its upper end similarly connected to a cam arm 42 rotatable on a fixed stud 44. When the treadle 30 is depressed against the force of the spring 32 the cam arm 42 engages a roll 46 on a rearwardly extending arm of a lever 43. The lever 48 is fulcrumed on a pin 50 supported in a bracket 52 secured to the machine frame and a forwardly extending arm of the lever 48 underlies a horizontal arm of a pawl lever forming a part of the stopping dog 22.

To enable the stopping dog to move laterally into and out of the path of the cam 20 the pawl lever is pivotally mounted on the sleeve 24 by pins 54 (FIGS. 4 and 6) secured in arms on the pawl lever and arranged at right angles to the axis of the sleeve, the inner ends of the pins engaging cylindrical sockets in the sleeve. The horizontal arm of the pawl lever forming part of the stopping dog 22 carries an abutment screw 56, which then the forward arm of the lever 48 is raised is engaged thereby to move the stopping dog about the pins 54 out of the path of the cam. This is the condition during normal running operation of the machine. When the treadle 30 is depressed the lever 43 is actuated by engagement of the cam arm 42 with the roll 46 to lift the forwardly extending arm of the lever 48 against the abutment screw 56. When the treadle is released and rises under the influence of the spring 32 a spring 58 stretched between the horizontal arm of the stopping dog 22 and a pin 60 (FIG. 4) fixed to the frame of the machine causes the stopping dog to be swung into the path of the cam 20 and the forward end of the lever 48 to be engaged and rocked downwardly by the abutment screw 56. To hold the lever 48 in engagment with the abutment screw 56 a spring 61 (see FIG. 3) is stretched between the forward arm of the lever and the machine frame, the spring 61 being weaker in its action than the spring 58 acting on the dog 22.

Shortly after the stopping dog 22 moves into the path of the cam 20 the enlargement on the cam shifts the stopping dog bodily within the path of the cam away from the sewing shaft. Such shift performs the auxiliary operations, such as raising the presser foot, through connections, including an arm 62 (FIGS. 4 and 6) forming a part of the sleeve 24 and a shoulder which engages the rear side of the stopping dog 22. The upper end of the arm 62 is connected through a link 64 to an upstanding arm of a lever 66 rotatable on a stud 68 secured in the frame of the machine. The upper end of the lever 66 engages an arm 70 fixed to a shaft 72, which is connected to the presser foot actuating mechanism. When the upper end of the lever 66 is moved rearwardly by the stopping dog the shaft 72 is rocked to raise the presser foot from engagement with the work and to perform the other auxiliary oprations, as more fully described in the Ashworth patent.

In bringing the machine to rest at the end of a seam it is highly desirable to have the machine reach its stopped position accurately with the needle and awl disengaged with the work and a last stitch in a seam completed. If either the needle or the awl are in engagement with the work when the machine reaches its stopped position and then an attempt is made to withdraw the work from the machine the engagement of the needle and awl with the work may injure them or the work itself may be disfigured or lacerated. Furthermore, upon restarting the machine the proper sequence of operations may not be performed during the first rotation of the sewing shaft, so that faulty stitches will be inserted.

To avoid these difliculties the present machine is provided with a stopping mechanism which insures bringing the machine to rest with the radial shoulder, indicated at 74 in FIG. 6, always in firm contact with the upper end of the stopping dog 22. To this end the sewing shaft 16 has mechanically connected to it the hydraulic displacement unit in the form of a vane type motor 76. The housing for the motor 76 is bolted directly to the frame of the machine outside a supporting bearing for the sewing shaft, and the motor is provided with inlet and outlet conduits 78 and 80 (see FIGS. 1, 2 and 11). As soon as the stopping dog 22 is moved into the path of the cam 26 the flow restricting circuit is connected to the motor outlet conduit 80 for bringing the stitch forming devices to rest in the desired stopped positions within a single rotation of the sewing shaft regardless of the speed of rotation. To dissipate the kinetic energy of the sewing shaft the flow restricting circuit includes an orifice 82 having an exhaust pipe 84 running to a sump 86, as shown in FIG. 11.

For connecting or disconnecting the orifice 82 with the motor outlet conduit 86 there is provided in circuit with the orifice a treadle actuated valve 88 joined to the outlet conduit through tubing 90, a section a of the valve and the orifice. When the machine is running the flow restricting circuit is rendered inoperative by a section b of the valve 88, the flow or" fluid through the tubing 90 running through the valve section b and a return to 92 in the exhaust pipe 84. To prevent connection of the orifice 82 with the motor outlet conduit there is provided a set of connections actuated in part by the movements of the stopping dog 22 after the control treadle has been released to bring the sewing shaft to rest and in part by the sewing shaft after having passed a point less than a minor fraction of a full rotation ahead of its stopped position, as will be explained more fully. For protecting the flow restricting circuit from damage by excessive pressures it is shunted by a high pressure relief valve 94.

To drive the machine at a variable speed depending upon the characteristics of the work operated upon, the motor 76 has an inlet conduit 78 connected with a hydraulic energy supply consisting of two rotary pumps 96 and 98, the pump 96 being constructed with large capacity displacement and the pump 98 with small capacity displacement. Both pumps have interconnected suction conduits 160 for drawing fluid through a strainer 102 disposed in the sump 86. Both pumps are driven from a common shaft by an electric motor 104 and have pressure outlet conduits 106 and 108 terminating in the inlet conduit 78 for the hydraulic motor 76. The small capacity pump 98 is effective in starting the machine or when running the machine at slow speed against heavy torque resistance, and the large capacity pump is operative above the speed at which the motor may be operated effectively by the small capacity pump. To render the large capacity pump inoperative at lower speeds the pressure outlet conduit 106 is connected with a low pressure relief valve 110 for venting into a drain 112 connected with the exhaust pipe 84.

To control rotation of the hydraulic motor 76 the pressure side of the large capacity pump is connected through a variable pressure compensated control valve 114 to by-pass into the exhaust pipe 84 a proportion of fluid from that pump determined by the position of the valve 114, the valve being actuated indirectly by the treadle lever 36. The flow of fluid from the low capacity pump is not by-passed by the valve 114, so that the motor 76 is continually driven in part by the pump 96, as will be described. To prevent flow of fluid from the small capacity pump 98 through the low pressure relief valve 110 when the large capacity pump is inoperative there is 7 connected between their pressure conduits a check valve 116.

After the main sewing shaft of the machine has been brought to rest with the presser foot disengaged from the work the load on both pumps 96 and 98 is released by venting their pressure conduits into the exhaust pipe 84. This is accomplished by a combination high pressure relief and solenoid actuated pilot valve 118, the construction of which is shown in FIG. 1t). As the presser foot is being raised at the end of a scam the lower end of the lever 66 is actuated forwardly and has secured to it a reversely bent plate 120 (see FIGS. 2, 4 and 6) carrying an abutment screw 122 (FIG. 2) arranged to engage a normally closed switch 124, in a manner to be described.

The switch 124, as shown in the circuit diagram of FIG. 12, is connected to the coil of a time delay relay 126 having normally open contacts 126K arranged in series with a solenoid coil 128, which when de-energized opens a duct 130 (FIG. 10) running from a valve seat 132, causing the relief valve to be opened and providing, through conduits 134 and 136, a vent for both pumps 96 and 98. The relief valve 118 also is adjustable for high pressure action by means of a thumb screw 138.

At the end of a seam when the auxiliary operation lever 66 is actuated, the time delay relay 126 has its coil circuit opened but does not open its contacts 126K until sufficient time has elapsed for the machine to come to rest with the shoulder 74 on the cam 20 in firm contact with the stopping dog 22. Thereafter the pressure produced by the pumps is vented and the machine may readily be rotated by means of the hand wheel 18 for adjusting or servicing purposes without interference.

To retain the auxiliary operation performing lever 66 in its actuated position while relieving the stopping dog 22 of pressure against the cam 20 without actually moving the dog out of the path of the cam, the auxiliary operation performing lever is held in position by a latch 14f) (FIG. 4) in the form of an arm fixed to the rearward end of a stud 142 and the latch is arranged to engage a projection on the lever 66, as more fully described in the Ashworth patent. To rotate the stud 142 in a direction to carry the latch 140 into latching position the stud has fixed to its forward end a horizontal arm 144 provided with an adjusting screw 146 which bears against the horizontal arm of the stopping dog 22. The arm 144 has projecting rearwardly from it a pin 148 between which and the pin 60 is stretched a spring 150. As soon as the control treadle is depressed and the machine is started in operation on a new shoe, movement of the lever 48 raises the horizontal arm of the stopping dog 22 and also the arm 144 to release the auxiliary operation lever 66 from the latch 140.

To prevent the stopping dog 22 in the illustrated machine from being moved yieldingly into the path of the cam 20 and from being engaged by the shoulder 74 of the cam with excessive violence, the stopping dog 22 has rotatably mounted within a horizontal bearing a releasable blocking arm 151 shown in FIGS. 4 to 7, inclusive. The blocking arm has a spindle passing through the hearing in the stopping dog and a finger projecting forwardly into the path of the cam 20 at such position as to be engaged by the shoulder 74 while the stopping dog is out of the path of the cam. To retain the blocking arm in locking position the spindle is surrounded by a coil spring 152 (FIGS. and 7), the ends of which engage openings in the spindle and in the stopping dog. Thus, with the positions of the parts shown in FIG. 6 the finger of the blocking arm holds the stopping dog out of the path of the cam while the shoulder on the cam is only a minor fraction of a full rotation in advance of the point where it engages the dog. To prevent the stopping dog from being released by the blocking arm before the treadle is released at the end of the seam both the dog and the blocking arm are held out of the path of the cam 20 and the finger portion of the arm is confined in a slot 153 to limit its rotation about its bearing in the dog.

Within a minor fraction of a full rotation of the cam there would be insufficient time to reduce the speed of the shaft adequately to prevent a destructive impact of the shoulder against the stopping dog, so that the cam is permitted to continue rotation for such minor fractional rotation until after the shoulder 74 passes the stopping dog and then the shoulder engages the finger of the blocking arm or latch 151. The blocking arm or latch has an upstanding lug 154 engaged by a portion of the arm 62 to prevent the stopping dog from moving into the path of the cam. Before the blocking arm is moved into the path of the cam and is engaged by the shoulder 74 it assumes the position of FIGS. 6 and 7. After releasing the stopping dog the blocking arm assumes the position of FIGS. 4 and 5, whereupon the stopping dog is permitted to move into the path of the cam. Thereafter, the sewing shaft 16 turns through a major fraction of a rotation (270) before the shoulder engages the stopping dog. During this major fraction of rotation the sewing shaft is retarded by the action of the flow restricting circuit and by the time the shoulder engages the dog the rotation of the shaft is reduced to a safe speed for such engagement.

To cause the flow restricting circuit to be connected to the motor conduit at the same time the stopping dog 22 is moved into the path of the cam 20 the horizontal arm of the stopping dog, as shown in FIGS. 2 and 4, has an opening through which passes the lower end of a link 155. The upper end of the link 155, as shown in FIGS. 2, 3 and 4, is connected to the midportion of a leaf spring 156, one end of which is secured to the machine frame and the other end of which overlies a normally closed switch 158 (see FIGS. 2 and 12). The switch 158 closes a circuit through holding contacts 160K actuated by a relay coil 160 and also holds closed another circuit through a solenoid 162 secured to the machine from directly above the treadle actuated valve 88 (see also FIG. 3). The solenoid 162 has an armature bar 163 acting against a plunger 164 of the valve 88. The arrangement is such that the treadle actuated valve 88 is yieldingly urged to a position in which the orifice 82 is effective to retard rotation of the motor 76, but when the control treadle 30 is depressed to start the machine the lever 48 engages the plunger 164 of the valve 88 to bring section b of the valve into operative position, so that the orifice 82 is disconnected from the outlet of the motor 76. This is the condition during operation of the machine, the normally open contacts of a switch 166 having been closed by the lever 48 when the machine is started, to energize both the solenoid 162 and the coil of the relay 160. Upon release of the treadle 30 the rearward end of the lever 48 disengages the switch 166 and permits the switch contacts to open, but the switch 158 remaining closed causes the relay coil 160 and the solenoid 162 to remain energized through the contacts 160K. Energization of the solenoid 162 also causes the armature bar to engage and hold down the valve plunger 164 the flow restricting circuit, thereby rendered inoperative. As soon as the stopping dog 22 enters into the path of the cam 20, however, the horizontal arm of the lever forming the stopping dog is actuated downwardly, causing the leaf spring 156 to engage the normally closed switch 158, thereby to open the contacts of this switch and thus to de-energize both the relay coil 160 and the solenoid 162. De-energizing the solenoid 162 releases the plunger 164 of the treadle actuated valve 88 and renders the flow restricting circuit effective in the outlet conduit of the motor 76 through the section a of the valve 88. By the use of the flow restricting circuit the rotation of the sewing shaft is reduced to a safe speed for the engagement of the shoulder 74 on the cam 20 with the stopping dog 22.

To insure that the shoulder 74 on the cam 20 is brought into firm engagement with the stopping dog, the small capacity pump 98, not being controlled by the variable pressure valve 114, the motor 76 continues to rotate at a slow speed while the flow restricting circuit continues to be effective, until the shoulder engages the stopping dog. The effectiveness of control and the speed at which the shoulder engages the stopping dog are regulated by the adjustment of the pressure relief valve 118, which is maintained well above the pressure required to operate the relief valve 110. Thus, the pump 08 provides high pressure fluid at low capacity; whereas the pump 96 provides low pressure fluid at high capacity for high operating speeds.

Rotation of the sewing shaft is provided by the output of the pump 98 alone after the relief valve 110 is opened. Under preferred operating conditions the slow speed of the shaft before closing the relief valve 110 does not exceed 80 to 100 rpm. Such speed is substantially below that which would cause excessive impact, rebound or damage to the machine from the stopping dog 22. The speed of the main sewing shaft is thus reduced within substantially less than a single rotation and the machine is brought to rest with the final stitch of a seam completed and the essential auxiliary operations performed.

The construction of the pressure compensated operator control valve 114 is best shown in FIG. 9 of the drawings. This valve is commercially procurable as Special Unit #1441 R-412 from the Waterman Engineering Company, Evanston, Illinois. The valve is arranged to provide a constant flow of fluid through it for a given position of its control shaft. The body of the valve is indicated at 168 and the control shaft at 170. The control shaft has secured to it a pinion 172 meshing with the teeth on a segment 174 rotatable on a stud 176 secured to a plate 178 on the body 168. The segment 174 is pivotally connected to the lower end of an adjustable link 179 (FIG. 3) having at its upper end an elongated slot 180, within which slot 180 is loosely confined a pivot 181 secured in a rearwardly extending arm of the lever 36 which is actuated by the treadle 30. The purpose of the slot 180 in the link 179 is to enable the lever 48 of the control connections to be actuated before the machine is started, thereby rendering the flow restricting circuit inoperative and providing time for other preparations to be made before resuming operation of the machine.

The control shaft 170 for the pressure compensated operator controlled valve has secured to its inner end a cylindrical valve member 182 providing an angular end face for closing or gradually opening an outlet 183 according to the desires of the operator. The flow of fluid from the opening provided by the valve is maintained under constant pressure by means of a duct 184 connected between the outlet 183 and an orifice 185 in a cylinder 186. Within the cylinder 186 is a spring pressed piston 188 arranged to open or close a compensating valve opening 190 connected with an inlet 192 for the valve. For easy operation of the shaft 170 the cylindrical valve member 182 is backed by a thrust bearing 194. By the use of the compensating piston 188 a constant pressure differential is maintained between the sides of valve member 182 to cause a uniform volume of fluid to flow through the opening controlled by the valve member, so that regardless of the load applied by the stitch forming devices in the machine a uniform speed of rotation is maintained while a corresponding position is assumed by the operator controlled valve.

To release all back pressure on the pumps 96 and 98 when the machine has been brought to rest the combination pressure relief and solenoid actuated pilot valve 118 shown in FIG. is provided. This valve has a body 195 with inlet and outlet passages 196 and 198. Between these two passages is a main spring pressed valve 200 having a central orifice 201 for balancing the pressure at opposite sides. The pilot for the valve consists of a spring pressed ball 202, the spring for which is confined between the ball and the lower end of the thumb adjusting screw 138. When the pressure in the inlet passage 196 exceeds that required to lift the ball 202 from its seat, a pressure differential develops between the two sides of the piston 200, in spite of the orifice 201 and raises the piston from its seat to provide pressure relief. The same action occurs when the solenoid coil 128 is de-energized. This solenoid acts on a spring pressed plunger 204 to raise the plunger against the seat 132 connected by the duct to the outlet passageway 198. When the solenoid is de-energized the plunger 204 closes the pilot valve and a similar pressure differential occurs between the sides of the piston 200, venting all pressure in the system.

To provide convenient means for mounting and con-- meeting the pressure relief valves 110 and 118 in the circuit they are bolted to a manifold in the form of a plate 206 shown in FIG. 8. The plate has suitable passageways forming continuations of conduits 78, 106, 108, drain 112 and conduit 134 alined with those of the pressure relief valves and arranged with the proper circuit connections as shown in FIG. 11.

By the use of a hydraulic energy supply which may be varied in accordance with the desires of the machine operator and by the further use of a fully compensated constant flow operator controlled valve an extremely smooth control of the machine is afforded with minimum effort on the part of the operator. The lost motion slot in the treadle connections enables the control valve to be opened through the action of a spring 208 (FIG. 3) stretched between a pin on the link 179 and a fixed part of the machine frame. As soon as the operator controlled valve is fully opened the torque applied by motor 76 to the sewing shaft is that provided by the small capacity pump 98, the operator controlled valve being connected to the treadle 30 so that the machine continues to operate at slowspeed. After the treadle has been fully released the cam arm 42 enables the rearward arm of the lever 48 to rise and the machine to be brought to rest in the usual manner in its predetermined stopped position, the auxiliary operations being performed as usual.

To return leakage from the hydraulic motor 76 to the sump 86 a drain 210 is connected between the two- For controlling the electrical motor 104 a suitable start and stop circuit is provided. The motor is started by a normally open button operated switch 212 bridged by holding contacts 214K of a relay 214. To stop the motor a normally closed button operated switch 216 is opened, the motor circuit being closed in starting by relay contacts 214KK.

The nature and scope of the invention having been set forth and a particular embodiment having been disclosed, what is claimed is:

1. A sewing machine having stitch forming devices stopping means including, a main sewing shaft for actuating said devices, a positive mechanical stop to determine a stopping position for the main sewing shaft and a hydraulic displacement unit mechanically connected to the main sewing shaft and provided with inlet and outlet conduits, in which the stopping means also includes a flow restricting circuit connected for selective operation to the outlet conduit for bringing the sewing shaft to rest when rotating at its normal running speed at a position determined by the positive stop and within a single rotation of the sewing shaft.

2. A sewing machine, as in claim 1, in which there is provided a hydraulic energy supply connected with the inlet conduit of the displacement unit and a pressure compensated operator controlled valve acting to vary the speed of the sewing shaft and to cause the same uniform volume of fluid to flow through the inlet conduit regardless of the resistance offered by the displacement unit while a corresponding position is assumed by the operator controlled valve.

3. A sewing machine, as in claim 2, in which the hydraulic energy supply includes a pump and the operator 1 1 controlled valve is connected in the inlet conduit of the displacement unit to by-pass a proportion of the volume of fluid supplied by the pump as determined by the position of the operator controlled valve.

4. A sewing machine, as in claim 2, in which the hydraulic energy supply consists of two rotary pumps having their outlets connected to the displacement unit, a low pressure relief valve venting the outlet of one pump, a high pressure relief valve venting the outlet of the other pump, the operator controlled valve acting to by-pass fluid from the low pressure vented pump only.

5. A sewing machine, as in claim 4, in which a check valve is arranged between the pump outlets to prevent entry of high pressure fluid into the low pressure vented pump.

6. A sewing machine, as in claim 3, in which there is provided a set of connections actuated by the sewing shaft to render operative the flow restricting circuit after the operator controlled valve has been shifted to bring the sewing shaft to rest and the shaft has passed a point less than a single rotation ahead of its stopped position.

7. A sewing machine having stitch forming devices, a main sewing shaft for actuating said devices, stopping means including a cam on the sewing shaft having a radial shoulder, and a dog mounted in the machine and arranged to enter into the path of said cam and to be engaged with the shoulder when the shaft reaches a predetermined stopping position, a hydraulic motor mechanically connected to the main sewing shaft and provided with inlet and outlet conduits and variable hydraulic energy supplying means connected with the inlet conduit of the hydraulic motor to vary the rotation of the sewing shaft from a maximum possible speed to a safe predetermined minimum, in which the stopping means also includes means for preventing entry of the dog into the path of the shoulder when the sewing shaft is a minor fraction of a full rotation ahead of stopped position to insure reduction to the safe speed before engagement of the shoulder with the dog.

8. A sewing machine, as in claim 7, in which the means for preventing entry of the stopping dog into the path of the shoulder on the cam comprises a blocking arm mounted in the path of the cam at a position a minor fraction of full rotation of the cam in advance of the stopped position.

9. A sewing machine as in claim 8, in which there are a flow restricting circuit, a valve arranged to connect the flow restricting circuit to the outlet conduit of the motor to retard rotation of the sewing shaft to the predeermined minimum speed and means for preventing the valve from connecting the flow restricting circuit to the outlet eonduit until after the dog enters the path of the cam.

10. A sewing machine having stitch forming devices, a main sewing shaft for actuating said devices, stopping means including a cam on the sewing shaft provided with a radial shoulder, a dog mounted in the machine to be moved into or out of the path of said cam to enable the shaft to be brought to rest in a predetermined stopped position, and an enlargement on the cam to move the dog bodily within the path of the cam, a hydraulic motor mechanically connected to the main sewing shaft and provided with inlet and outlet conduits, a How restricting circuit arranged to be connected to the outlet conduit of the motor to bring the sewing shaft to rest with the stitch forming devices in a predetermined position and a valve it for connecting the flow restricting circuit to the outlet conduit, in which the stopping means also includes connections for actuating the valve to connect the flow restricting circuit to the conduit whenever the dog enters into the path of the cam and to prevent disconnection of the flow restricting circuit from the outlet conduit of the motor until after the dog is shifted bodily within the path of the cam as the sewing shaft reaches its stopped position.

11. A sewing machine, as in claim 10, in which there are provided an operator controlled treadle for shifting the dog into the path of the earn, the valve for connecting the flow restricting circuit to the outlet conduit of the hydraulic motor being of the electromagnetic type, a switch actuated by the treadle for energizing the electromagnetic valve and a second switch actuated by the bodily movement of the dog within the path of the cam for causing the valve to disconnect the flow restricting circuit from the outlet conduit of the motor.

12. A sewing machine, as in claim 11, in which there are provided a latch mounted in the path of the cam at a position less than a full rotation of the cam beyond the point where the shoulder is engaged by the dog to release the dog for movement into the path of the cam and a third switch and a solenoid actuated relief valve controlled by the third switch to vent the pressure applied to the motor after the dog is engaged by the shoulder on the cam.

13. A sewing machine having stitch forming devices, a main sewing shaft for actuating said devices, a hydraulic displacement unit mechanically connected to the sewing shaft and provided with inlet and outlet conduits, in combination with stopping means including a flow restricting circuit connected for selective operation to the outlet conduit for bringing the stitch forming devices to rest in predetermined stopped positions and hydraulic energy supplying means comprising a pair of pumps connected to the displacement unit, one of which pumps is of small capacity and the other of which is of large capacity.

14. A sewing machine, as in claim 13, provided with an operator controlled valve for by-passing the large capacity pump to regulate the sewing shaft at slower speed, the small capacity pump remaining effective to drive the hydraulic displacement unit at slowest speed.

15. A sewing machine, as in claim 14, in which the stopping means includes a positive mechanical stop for bringing the stitch forming devices to rest at predetermined stopped positions while the displacement unit is being driven by the small capacity pump.

16. A sewing machine, as in claim 15, in which the hydraulic flow restricting circuit acts on the hydraulic displacement unit before the positive stop becomes effective to reduce the rotation of the sewing shaft to a safe speed for engagement with the positive stop.

17. A sewing machine, as in claim 16, provided with means for venting the pressure of both pumps when the sewing shaft has been brought to rest.

References Cited in the file of this patent UNITED STATES PATENTS 1,233,539 Ashworth July 17, 1917 2,159,250 Brantly May 23, 1939 2,171,204 Vickers Aug. 29, 1939 2,681,717 Spurgeon June 22, 1954 

1. A SEWING MACHINE HAVING STITCH FORMING DEVICES STOPPING MEANS INCLUDING, A MAIN SEWING SHAFT FOR ACTUATING SAID DEVICES, A POSITIVE MECHANICAL STOP TO DETERMINE A STOPPING POSITION FOR THE MAIN SEWING SHAFT AND A HYDRAULIC DISPLACEMENT UNIT MECHANICALLY CONNECTED TO THE MAIN SEWING SHAFT AND PROVIDED WITH INLET AND OUTLET CONDUITS, IN WHICH THE STOPPING MEANS ALSO INCLUDES A FLOW RESTRICTING CIRCUIT CONNECTED FOR SELECTIVE OPERATION TO THE OUTLET CONDUIT FOR BRINGING THE SEWING SHAFT TO REST WHEN ROTATING AT ITS NORMAL RUNNING SPEED AT A POSITION DETERMINED BY THE POSITIVE STOP AND WITHIN A SINGLE ROTATION OF THE SEWING SHAFT. 